“I always smile when I hear Garrison Keillor say, ‘Be well, do good work, and keep in touch,’ ” Gazzaniga writes. In that one sentence, “Keillor captures humanness.” In his own easy-to-read, conversational style, Gazzaniga, a neuroscientist at the University of California, Santa Barbara, and author of a slew of popular books, takes off in search of what set humans apart from their predecessors. His entertaining tour includes some of the most lucid explanations of scientific concepts around as well as discursions into art, aesthetics, empathy, ethics, cyborgs, animals on trial and what it would be like to date a chimp. Neuroscience has focused on the brain systems underlying possible decisive traits that are uniquely human—language, memory, emotion—but it has not usually considered the point Keillor intuitively conveys: most of the time humans are thinking about social relationships. We really do want to stay in touch.

Okay, so you’re not an idiot. You’ll still like this guide to string theory. First, the easy-to-follow review of relativity, quantum mechanics, the Standard Model, the possibility of time travel, and much more. Then, the way alternatives to string theory play a role. And, crucially, the fluent understanding of the concepts, conveyed in everyday, even breezy, language. String theory, the leading proposal for unifying relativity and quantum theory, interprets subatomic particles as tiny vibrating strings. Tiny, Musser (who is an editor and writer at this magazine) emphasizes, is really tiny. The relation of a string to an atom is the same as that of a human to the entire visible universe.
The next few years will be critical for string theory. The Large Hadron Collider (LHC), “the world’s most powerful and most expensive hammer,” will begin to smash particles into bits to see what they are made of and to give new types a chance to form. But despite the promise of the LHC, unification, Musser warns, won’t be a matter of solving equations and filling in details. Finishing the job will require new conceptual input.

Susskind, a professor of theoretical physics at Stanford University, delivers a beautifully written account of the battle over the true nature of black holes that he and Dutch physicist Gerard ’t Hooft have waged with Stephen Hawking:

“In 1976 Stephen Hawking imagined throwing a bit of information—a book, a computer, even an elementary particle—into a black hole. Black holes, Hawking believed, were the ultimate traps, and the bit of information would be irretrievably lost to the outside world. This apparently innocent observation was hardly as innocent as it sounds; it threatened to undermine and topple the entire edifice of modern physics. Something was terribly out of whack; the most basic law of nature—the conservation of information—was seriously at risk. To those who paid attention, either Hawking was wrong or the three-hundred-year-old center of physics wasn’t holding....

“The Black Hole War was a genuine scientific controversy—nothing like the pseudo­debates over intelligent design, or the existence of global warming. Those phony arguments, cooked up by political manipulators to confuse a naive public, don’t reflect any real scientific differences of opinion. By contrast, the split over black holes was very real.... It was not a war between angry enemies; indeed the main participants are all friends. But it was a fierce intellectual struggle of ideas between people who deeply respected each other but also profoundly disagreed.”